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Millbrae Avenue over U.S. Highway 101

San Mateo County, California · rated Fair in the 2025 National Bridge Inventory

United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled August 20, 2026

Millbrae Avenue over U.S. Highway 101 in San Mateo County, California, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the deck, rated 5 (fair condition) on the 0-9 scale.
It was built in 1947 and reconstructed in 1976, making it 78 years old at the 2025 inventory.
It carries about 53,747 vehicles a day (traffic count year 1999).
Its listed owner is the state highway agency.
It is one of 224 of the 361 inventoried bridges in San Mateo County rated fair (62.0%); 37 (10.2%) are rated poor.
A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.

Component ratings


Structure	Steel stringer or multi-beam girder
Length	about 815 ft
Location	04-sm-101-17.95-mlbr
NBI structure number	35 0089
Condition class	Fair

Source: FHWA National Bridge Inventory, 2025 data as reported by the California department of transportation.

Bridge	Built	Vehicles/day	Condition
U.S. Highway 101 over San Mateo Creek	1928	236,000	Good
US 101 Rollins Rd over Transmission Canal	1928	232,000	Fair
US 101 Mcdonnell over Millbrae Slough	1947	226,000	Fair
US 101 W&e Bayshr over San Francisquito Creek	2018	225,800	Good
Holly Street over US Highway 101	1954	201,000	Fair
Whipple Avenue over US Highway 101	1958	201,000	Good